The primary goal of the Trace Element Analysis (TEA) Core (Core B) is to provide specific analytical services and analytical expertise to Dartmouth SBRP researchers to allow them to successfully complete the aims of their individual projects. Additionally, the TEA Core strives to be at the forefront of (mission-related) method development that augments the themes of the Dartmouth SBRP projects and advances these projects by providing analytical advances such as lower detection limits, quantification of an as yet unmeasured metal species, or the novel application of an analytical methodology. The TEA Core utilizes state of the art analytical instrumentation based on inductively coupled plasma mass spectrometry (ICP-MS) to provide low level determinations of trace elements in a variety of biological and environmental matrices. The TEA Core also provides speciation analysis for arsenic and mercury by liquid chromatography and gas chromatography coupled to ICP-MS, respectively. The chemical form (species) of arsenic or mercury in a sample ultimately determines the toxicity of that element, hence speciation information is essential in assessing the human health effects of these ubiquitous contaminant elements. The TEA Core provides toenail and hair analysis to assess the exposure of an individual to trace metals. Methods have been developed to quantify six chemical species of arsenic in human urine;these species range from arsenobetaine, a non-toxic form of arsenic that people are routinely exposed to through seafood, to monomethlarsenous acid, MMA(III), an extremely toxic chemical form of arsenic. The TEA Core also provides methodology to speciate mercury at extremely low levels and in very small sample masses. Our GC-ICP-MS methods can detect less than 1 picogram of mercury and can determine mercury species in sub milligram sample weights. Methylmercury is an extremely toxic form of mercury that bioaccumulates through the food chain, hence it is essential to be able to determine this mercury species at very low levels. The TEA Core continues to push the boundary of low level trace element detection to develop and validate methods for the determination of trace elements or elemental species in biological samples with the goal of providing Dartmouth SRBP researchers the information they need to make better predictive decisions about human and ecosystem health.